Methods are known in which a measurement has to be performed outside a running manufacturing process, because the techniques used do not allow for a real-time measurement.
However, DE 198 45 363 A1 discloses a laser measuring device for on-line measurement of particle size distributions in manufacturing processes. The measuring method is performed in accordance with the “time of transition” principle, wherein a laser beam is highly focused and scanned over the particles to be measured by a deflection unit. The laser radiation is collected behind the measurement plane and measured by a detector. If the deflected beam hits a particle, it is temporarily interrupted. The particle size can be calculated from the duration of this interruption and the known deflection velocity of the beam.